Zhang X, Rosenstein B S, Wang Y, Lebwohl M, Wei H
Department of Dermatology, Mount Sinai School of Medicine, City University of New York, New York 10029, USA.
Free Radic Biol Med. 1997;23(7):980-5. doi: 10.1016/s0891-5849(97)00126-3.
We have previously demonstrated that each region of the ultraviolet (UV) spectrum (UVA, UVB, and UVC) induces the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in purified calf thymus DNA and HeLa cells in a fluence-dependent manner. In the present study, we further characterize the possible reactive oxygen species (ROS) that are involved in the induction of 8-oxodGuo by UV radiation. Sodium azide, a singlet oxygen (1O2) scavenger though its quenching effect on HO. was also reported, inhibited 8-oxodGuo production in calf thymus DNA exposed to UVA, UVB, or UVC in a concentration-dependent fashion with maximal quenching effect of over 90% at a concentration of 10 mM. Catalase, at a concentration of 50 U/ml, reduced the yields of UVA- and UVB-induced 8-oxodGuo formation by approximately 50%, but had little effect on UVC-induced 8-oxodGuo production. In contrast, 50 U/ml of superoxide dismutase (SOD) did not affect induction of 8-oxodGuo by any portion of the UV spectrum. Hydroxyl radical (HO.) scavengers mannitol and dimethylsulfoxide (DMSO) moderately reduced the levels of 8-oxodGuo induced by UVA and UVB, but not those by UVC. Instead, mannitol and DMSO enhanced the formation of 8-oxodGuo induced by UVC. These results suggest that certain types of ROS are involved in UV-induced 8-oxodGuo formation with 1O2 playing the predominant role throughout the UV spectrum. Except for UVC, other ROS such as hydrogen peroxide (H2O2) and HO. may also be involved in UVA- and UVB-induced oxidative DNA damage. Superoxide anion appears not to participate in UV-induced oxidation of guanosine in calf thymus DNA, as SOD did not display any quenching effects.
我们之前已经证明，紫外线（UV）光谱的每个区域（UVA、UVB和UVC）都能以剂量依赖的方式在纯化的小牛胸腺DNA和HeLa细胞中诱导8-氧代-7,8-二氢-2'-脱氧鸟苷（8-氧代dGuo）的形成。在本研究中，我们进一步表征了可能参与紫外线辐射诱导8-氧代dGuo形成的活性氧（ROS）。叠氮化钠是一种单线态氧（1O2）清除剂，尽管其对羟基自由基（HO·）也有淬灭作用，据报道，它能以浓度依赖的方式抑制暴露于UVA、UVB或UVC的小牛胸腺DNA中8-氧代dGuo的产生，在10 mM浓度下具有超过90%的最大淬灭效果。浓度为50 U/ml的过氧化氢酶可使UVA和UVB诱导的8-氧代dGuo形成产量降低约50%，但对UVC诱导的8-氧代dGuo产生影响不大。相比之下，50 U/ml的超氧化物歧化酶（SOD）对紫外线光谱任何部分诱导的8-氧代dGuo均无影响。羟基自由基（HO·）清除剂甘露醇和二甲基亚砜（DMSO）可适度降低UVA和UVB诱导的8-氧代dGuo水平，但对UVC诱导的8-氧代dGuo水平无影响。相反，甘露醇和DMSO会增强UVC诱导的8-氧代dGuo的形成。这些结果表明，某些类型的ROS参与了紫外线诱导的8-氧代dGuo形成，其中1O2在整个紫外线光谱中起主要作用。除UVC外，其他ROS如过氧化氢（H2O2）和HO·也可能参与UVA和UVB诱导的氧化性DNA损伤。超氧阴离子似乎不参与紫外线诱导的小牛胸腺DNA中鸟苷的氧化，因为SOD未显示任何淬灭作用。
